[SeaBIOS] [PATCH 05/12] Track when entering via call32() and use the same mode for stack_hop_back()
Kevin O'Connor
kevin at koconnor.net
Tue Sep 30 20:38:39 CEST 2014
If 32bit mode is entered directly via transition32, then use a simple
call16() when hopping back to 16bit mode. Use only call16big() when
entering 32bit mode via call32().
Signed-off-by: Kevin O'Connor <kevin at koconnor.net>
---
src/stacks.c | 27 ++++++++++++++++++++++++++-
1 file changed, 26 insertions(+), 1 deletion(-)
diff --git a/src/stacks.c b/src/stacks.c
index 5a2628a..5674d0a 100644
--- a/src/stacks.c
+++ b/src/stacks.c
@@ -22,6 +22,8 @@
****************************************************************/
u16 StackSeg VARLOW;
+u8 Call32Method VARLOW;
+#define C32_SLOPPY 1
// Call a 32bit SeaBIOS function from a 16bit SeaBIOS function.
u32 VISIBLE16
@@ -45,6 +47,7 @@ call32(void *func, u32 eax, u32 errret)
u16 oldstackseg = GET_LOW(StackSeg);
SET_LOW(StackSeg, GET_SEG(SS));
+ SET_LOW(Call32Method, C32_SLOPPY);
u32 bkup_ss, bkup_esp;
asm volatile(
// Backup ss/esp / set esp to flat stack location
@@ -71,6 +74,7 @@ call32(void *func, u32 eax, u32 errret)
: "r" (func)
: "ecx", "edx", "cc", "memory");
+ SET_LOW(Call32Method, 0);
SET_LOW(StackSeg, oldstackseg);
// Restore gdt and fs/gs
@@ -95,6 +99,7 @@ call16(u32 eax, u32 edx, void *func)
return __call16(eax, edx, func - BUILD_BIOS_ADDR);
}
+// Call a 16bit SeaBIOS function in "big real" mode.
static inline u32
call16big(u32 eax, u32 edx, void *func)
{
@@ -105,6 +110,26 @@ call16big(u32 eax, u32 edx, void *func)
return __call16big(eax, edx, func - BUILD_BIOS_ADDR);
}
+// Jump back to 16bit mode while in 32bit mode from call32()
+static u32
+call16_sloppy(u32 eax, u32 edx, void *func)
+{
+ Call32Method = 0;
+ u32 ret = call16big(eax, edx, func);
+ Call32Method = C32_SLOPPY;
+ return ret;
+}
+
+// Call a 16bit SeaBIOS function, restoring the mode from last call32().
+static u32
+call16_back(u32 eax, u32 edx, void *func)
+{
+ ASSERT32FLAT();
+ if (Call32Method == C32_SLOPPY)
+ return call16_sloppy(eax, edx, func);
+ return call16(eax, edx, func);
+}
+
/****************************************************************
* Extra 16bit stack
@@ -159,7 +184,7 @@ u32
stack_hop_back(u32 eax, u32 edx, void *func)
{
if (!MODESEGMENT)
- return call16big(eax, edx, func);
+ return call16_back(eax, edx, func);
if (!on_extra_stack())
return ((u32 (*)(u32, u32))func)(eax, edx);
ASSERT16();
--
1.9.3
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